The goal of this proposal is to design, implement, and evaluate a user interface based on natural language input that will enable health care professionals to access information for clinical, scholarly, and administrative purposes. The significance of the interface is that it is simple for busy professionals to learn the first time, easy for intermittent users to remember, and very general. The specific aims are: (1) provide users of a medical information system a simple and general interface for accessing information; (2) enable access to a broad range of information resources; and (3) evaluate the user interface in terms of its generality, reliability, and usability. The research design is iterative - assessing the system each year, and using the results of these evaluations to improve performance. The first part of Year 1 will be used to develop the preliminary natural language interface consisting of: a workstation interface that will allow a user to enter information requests in natural language and review the results; a natural language parser that will analyze the user's information request and produce a formal representation of its medical information content; and a natural language generator that will provide feedback to the user in simple English concerning the extent of the system's understanding of the information request. The latter part of Year 1 will be used to develop a resource mediator, that will interpret the user's request and interact with information resources on the user's behalf. The resource mediator will provide access to a database of the medical literature (MEDLINE), and a database of pharmaceutical information (Physician's Desk Reference). In addition, the resource mediator will provide feedback to the user about access limitations to information resources, e.g., that certain data is not available, or requires special authorization. At the beginning of Year 2, the reliability of the interface will be assessed by having experts in MEDLINE searching rate its performance in interpreting natural language and in accessing the medical literature. The results of this study will be used to enhance the natural language components. The remainder of the year will be spent on enabling the resource mediator to access a database of clinical information (CPMC Clinical Database). In the following three years, the reliability study will be conducted in the beginning of the year, using experts for all three information resources. In addition, an evaluation will be performed each year to assess the usability of the system as a whole. This study will compare the ability of health-care professionals to access information using the natural language interface against their ability to access information using a high-level access language (conceptual graphs). These studies will be used to make enhancements in the natural language components and resource mediator.